Turing's machine and Bletchley Park

In 1928 the mathematician David Hilbert asked whether there could be a mechanical procedure that decides, for any mathematical statement, whether it is true. To answer, someone first had to say precisely what a mechanical procedure is.

Alan Turing, a young Cambridge mathematician, did it in a paper published in the Proceedings of the London Mathematical Society at the end of 1936: “On Computable Numbers, with an Application to the Entscheidungsproblem”. His answer to Hilbert was no. The way he got there described, in a few pages, the machine that every computer would turn out to be.